This invention relates to a method of recovering cyclic arylene sulfide oligomers from a solution comprising poly(arylene sulfide) polymer and a polar organic compound.
Poly(arylene sulfide) polymers are known in the art and have found wide use due to their desirable thermal and Chemical resistance. Poly(arylene sulfide) polymers are useful in the formation of films, fibers, composites and molded parts by a variety of methods known to those of skill in the art.
Oligomers and polymer by-products in poly(arylene sulfide) polymer products may contribute to certain processing and final product problems. Problems attributed to high oligomer concentrations in the polymer include mold plate out, die face build up, exhaust duct fouling, bubble formation in molded parts, corrosion, injection molding drool and off gassing during injection molding. Solvent extraction methods can be used to remove some of the oligomers and other impurities from poly(arylene sulfide) products.
Other impurities might include, for example, unreacted dihaloaromatic compounds, tri- or tetrahaloaromatic compounds, residual polar organic compounds, inorganic salts, or other by-products associated with poly(arylene sulfide) polymerization or recovery.
When past attempts have been made to remove non-polymeric impurities, cyclic and linear oligomers from s poly(arylene sulfide) polymer or polymerization mixture, difficulties have been experienced in filtering the oligomer solids, primarily due to the extremely fine particle size and tackiness of the cyclic oligomers. It would be desirable to have an easier method for removing and recovering nonpolymeric impurities and oligomers.
Once the oligomers and impurities are removed from the poly(arylene sulfide) polymer, they must be disposed of in some manner. It has recently been discovered that cyclic oligomers can be used as a reactant in a subsequent poly(arylene sulfide) polymerization. However, no simple and effective method has existed to recover cyclic oligomers from linear oligomers and other impurities removed from a poly(arylene sulfide) polymer or spent: polymerization reaction mixture.
It is an object of this invention to provide a method for recovering cyclic oligomers from a poly(arylene sulfide) polymer, or spent polymerization reaction mixture, or recovering cyclic oligomers from admixture with linear oligomers and impurities removed from a poly(arylene sulfide) polymer or spent polymerization reaction mixture.